Prior art hole saws having outer diameters of 1¼ inches or greater typically include an end portion defining a threaded aperture and at least two drive pin apertures. The hole saws are coupled to desired power tools or machines via arbors, which typically include threaded end portions that engage the saws' threaded apertures, and drive pin plates having drive pins that extend into the saws' drive pin apertures. When mounting a hole saw of this variety to an arbor, the saw is threaded onto the arbor's end portion until the saw is secured to the arbor body and the drive pin apertures align with the corresponding drive pins of the arbor's drive pin plate. The drive pin plate is then moved toward the saw until the drive pins are received within the drive pin apertures. With this arrangement, the hole saw is driven off of the drive pins as opposed to the arbor's threads, thereby reducing the possibility that the saw will lock up on the arbor's threads during use or otherwise damage the threads.
Because of their smaller size, conventional hole saws having outer diameters of less than 1¼ inches (i.e. “small diameter hole saws”) and the arbors used to drive such small diameter hole saws do not have sufficient room for, and therefore do not include drive pin apertures and drive pins, respectively. Consequently, typical arbors used to drive such smaller diameter hole saws do not include drive pins and, as a result, typically drive the hole saws with the threaded end portions of the arbors. A significant drawback of this configuration is that the hole saw can lock up on the threads during use which, in turn, makes it exceedingly difficult if not impossible to remove the saw from the arbor. When confronted with a hole saw that is locked up on its arbor's threads, users may choose to sacrifice the arbor (i.e., dispose of the arbor prematurely with the locked up hole saw attached) to avoid the difficult and time consuming task of separating the arbor from the hole saw. Further, even if the hole saw is successfully removed from the arbor, the task of removing a locked up hole saw can result in permanent damage to the arbor and/or hole saw threads.
To assist users in removing locked up small diameter hole saws, prior art hole saws have been devised with wrench flats on the end caps of the hole saws to allow users to employ tools, such as wrenches, to remove such hole saws when locked up on the threads of an arbor. A typical such group of prior art hole saws is shown in FIG. 14. However, even with the inclusion of wrench flats, the engaging threads of the hole saws and/or arbors can be stripped and/or damaged beyond repair when users attempt to unlock and remove the saws from the arbors. Furthermore, the Applicant is not aware of any teaching or suggestion in the prior art to drive small diameter hole saws off of the wrench flats. And, even if one were to devise an arbor for driving a small diameter hole saw from the wrench flats (and Applicant is not aware of any such teaching or suggestion in the prior art), the arbor would not be compatible with all sizes of small diameter hole saws (i.e., the arbor could not drive from the flats) because the widths between the wrench flats differ among many different sizes of the small diameter hole saws, typically increasing as the size of the hole saw increases. In the exemplary group of prior art hole saws shown in FIG. 14, the distance between the wrench flats for the illustrated hole saws varies as follows:
Prior Art⅞inch 15/16inch1inch1⅙inch1⅛inchHole SawDiameterDistance0.620inch0.750inch0.745inch0.870inch0.870inchBetweenWrenchFlats
Three of the most popular sized small diameter hole saws are the ⅞ inch diameter hole saw, the 1 inch diameter hole saw, and the 1⅛ inch diameter hole saw. As can be seen, in the exemplary prior art set of small diameter hole saws, each of these most popular hole cutters defines a different width or distance between the wrench flats. Accordingly, even if one desired to drive such hole saws from the wrench flats (which Applicant does not believe is taught or suggested by the prior art), because the wrench flats of such popular sizes define different widths between the flats, the same arbor could not be used to drive the different sized hole saws. Other hole saws in such exemplary set of prior art small diameter hole saws include an 11/16 inch diameter hole saw, a ¾ inch diameter hole saw, a 25/32 inch diameter hole saw, a 13/16 inch diameter hole saw, and a 1 3/16 inch diameter hole saw. These hole saws having diameters between 11/16 inch and 13/16 inch define widths between wrench flats of about 0.620 inch or about 0.625 inch, and the 1 3/16 inch diameter hole saw defines a width between the wrench flats of about 0.995 inch.
Another drawback of prior art small diameter hole saws is that, without the aid of drive pins, the arbors can fail to properly secure the saws during use, particularly in cases where the hole saws are not correctly threaded onto the associated arbors. This failure results in off-axis wobble, especially at high rotational speeds. Off-axis wobble can cause undesirable vibrations of the saw during use which, in turn, can reduce the life of the saw and/or create an unacceptable degree of cutting inaccuracy.
Another drawback of prior art small diameter hole saws is that multiple revolutions are required to threadedly attach and remove the hole saws to and from the arbors. Further, when attaching the hole saws, the hole saw threads must be properly aligned and threadedly engaged with the arbor threads to avoid off-axis wobble (as discussed above) and to prevent the arbor threads and/or hole saw threads from stripping, which can render the arbor and/or hole saw unusable.
Accordingly, it is an object of the present invention to overcome one or more of the above-described drawbacks and/or disadvantages of prior art small diameter hole saws and arbors.